The invention relates to a support assembly with a deformation element, in particular for a motor vehicle, for absorbing kinetic energy during an impact.
Deformation elements for absorbing kinetic energy are used in an extremely wide range of engineering applications. One particular area of application for elements of this kind is in motor vehicles. The technical and safety standards require that, in the case of minor impacts, the impact energy should be absorbed in an essentially elastic manner by corresponding elements and, in the case of more severe impacts, e.g. in the case of accidents, the kinetic energy should be absorbed by such elements and converted into deformation of the latter. Thus, for example, the prior art includes deformation elements which are used for longitudinal members of a vehicle and which remain undamaged in the event of an impact up to 4 km/h and, in the case of an impact up to 15 km/h, absorb the entire kinetic energy and convert it into deformation. In general, such deformation elements are integrated into the longitudinal members to form a unitary supporting structure, with the result that the entire longitudinal member has to be replaced in the event of damage. The requirement that essentially the entire kinetic energy should be absorbed by the deformation elements without a significant proportion of this deformation energy being transmitted to the other structures of a motor vehicle is one that must also be satisfied with a view to increasing the survival chances of people in vehicles that are involved in an accident.
Honeycomb structures are used in many different ways for various applications in engineering. For example, honeycomb structures are used in the construction of aircraft, where requirements for lightweight construction and high strength, in particular, are important. Honeycomb structures are also known from areas where it is not so much the strength of such a honeycomb structure as increasing the surface area which is important, e.g. in the case of catalyst substrates in the exhaust system of a motor vehicle for removing the noxious exhaust components that remain in the exhaust after combustion in the engine.
German Utility Model G 89 00 467 U1, European Patent Application 0 389 750 A1, UK Patent Application GB 2 029 720 A, German Published, Non-Prosecuted Patent Application DE 40 24 942 A1, German Patent DE 38 09 490 C1 and German Published, Non-Prosecuted Patent Application DE 44 45 557 A1, corresponding to U.S. application Ser. No. 08/879,594, filed Jun. 20, 1997, have disclosed various configurations and structures for honeycomb bodies. In general, these honeycomb bodies that have been described are used to improve the flow characteristics in the matrix body""s channels, which are configured as flow channels, in order to obtain improved chemical reactions. The jacketing configurations surrounding the actual matrix body are used to absorb the high thermal loads to which catalyst substrates of this kind are exposed in the exhaust system of a motor vehicle.
German Published, Non-Prosecuted Patent Application DE 196 50 647 A1 has disclosed a deformation element for a motor vehicle, in which a honeycomb body that is known per se and disposed in a jacketing tube is used as a deformation element.
One disadvantage with the known deformation elements is that they are either integrated completely into the supporting structures, necessitating replacement of the entire supporting structure in the event of damage, or, where deformation elements with a honeycomb structure are used, a steep rise in the curve describing the deformation force/deformation path profile (F,s profile) occurs relatively quickly if high kinetic energy is introduced, which means that the high deformation forces that occur are transmitted directly into the supporting structure. Another disadvantage is that the known deformation elements with a honeycomb structure have a jacketing configuration which may also affect the deformation behavior to a considerable extent, possibly in a disadvantageous way.
It is accordingly an object of the invention to provide a support assembly having a deformation element which overcomes the above-mentioned disadvantages of the heretofore-known support assemblies of this general type and which, compared with conventional support assemblies having deformation elements, ensures a desired deformation force/deformation path profile (F,s profile), which in particular meets respective application-specific requirements, and which minimizes the effect of a jacketing configuration on the deformation behavior and which can be used, in particular, for vehicle bumper systems.
With the foregoing and other objects in view there is provided, in accordance with the invention, a support assembly for a motor vehicle, including:
a supporting structure;
a deformation element for absorbing kinetic energy during an impact, the deformation element being connected to the supporting structure and being deformable as far as a residual length, and the deformation element including a honeycomb matrix body;
the honeycomb matrix body being a self-supporting configuration and having at least two axial partial regions spaced from one another;
the honeycomb matrix body including at least one radial deformation limiter disposed in the at least two axial partial regions of the matrix body; and
the honeycomb matrix body having a first axial rigidity and the at least one radial deformation limiter having a second axial rigidity smaller than the first axial rigidity.
In other words, the support assembly according to the invention has a deformation element, in particular for motor vehicles, for absorbing kinetic energy during an impact. When the kinetic energy is introduced, the deformation element can be deformed as far as a residual block length and is connected to the supporting structure. The deformation element includes a honeycomb matrix body. According to the invention, the deformation element is a self-supporting configuration, i.e. the matrix body has adequate rigidity. Moreover, the matrix body of the deformation element is surrounded by at least one radial deformation limiter with a low axial rigidity.
The task of a radial deformation limiter of this kind is to prevent a situation where, as kinetic energy is introduced into the deformation element, the matrix body of the latter is severely deformed in the radial direction or in a direction that differs from the longitudinal axis of the matrix body assigned to the deformation element when the latter is deformed. Sideways displacement of parts of the matrix body during its longitudinal deformation, away from the longitudinal axis of the deformation element, results in non-compliance with the desired deformation properties for which the deformation element was configured since, in such a case, there is no guarantee that the deformation element will be able to absorb the kinetic energy. Radial deformation limiters are therefore provided around the outside of the matrix body and these ensure that the matrix body is deformed and crushed essentially only within its original volume when forces act on it in an axial or even somewhat lateral direction. However, the radial deformation limiters are dimensioned in such a way that in other respects they have as little effect as possible on the deformation behavior of the deformation element and therefore its F,s profile.
The deformation behavior of the deformation element should be determined essentially by the matrix body alone. A jacketing configuration constructed from a relatively strong material completely surrounding the outside of the matrix body in the form of a sleeve or jacket has a relatively great effect on the deformation behavior. The less effect the radial deformation limiters have on the deformation behavior of the deformation element, the more effectively can the specific construction of the matrix body, including its dimensioning, be used to ensure an application-specific F,s profile.
In accordance with another feature of the invention, the at least one radial deformation limiter is a jacket, which at least partially surrounds the honeycomb matrix body.
In accordance with yet another feature of the invention, the second axial rigidity and the first axial rigidity have a ratio of between 1:5 and 1:50 and preferably of less than 1:10.
According to a first exemplary embodiment, the radial deformation limiter is preferably configured as a jacketing configuration with a low axial rigidity which surrounds the matrix body and is preferably in the form of spaced jacketing rings. In this configuration, the purpose of the jacketing rings is to act as radial deformation limiters without representing a disturbing variable for the deformation behavior during the compression of the matrix body of the deformation element.
According to another exemplary embodiment, the radial deformation limiter is configured as a bellows-type corrugated hose with predetermined buckling points. In this configuration, the inside diameter of the corrugated hose is dimensioned in such a way that the troughs of its corrugations essentially touch the circumferential surface of the matrix body. A bellows-type corrugated hose of this kind can be deformed easily, especially in the axial direction, with the result that, when the matrix body is deformed essentially in its longitudinal direction to absorb kinetic energy, the corrugated hose does not make any significant contribution to the absorption of the kinetic energy. The presence of predetermined buckling points in the bellows-type corrugated hose ensures that, as the matrix body is compressed in its longitudinal direction, the individual corrugations of the corrugated hose are, as it were, folded up against one another.
The residual block length of the jacketing configuration which is theoretically obtained when the deformation element is deformed completely is preferably less than or at most equal to the residual block length of the matrix body. This ensures that the radial deformation limiters have no significant effect on the deformation behavior and hence on the F,s profile in the case of complete deformation.
According to another exemplary embodiment, the corrugations of the corrugated hose of the jacketing configuration are configured in such a way that they act as initiators for buckles and/or folds in the radial deformation limiter at the beginning of the deformation process. These initiators ensure that, at the beginning of the deformation process in particular, the initial peak present in the F,s profile is not increased by the radial deformation limiters. On the contrary, the matrix body is configured in such a way that the initial peak in the F,s profile in particular is at least moderate or is preferably completely eliminated.
According to another exemplary embodiment of the invention, at at least one end at which there is a support or support region on the supporting structure, the deformation element is provided with a perforated plate with at least one hole. The at least one hole in the perforated plate is dimensioned in such a way that parts of the matrix body situated in the area of the hole can be displaced into the hole or through the hole in the direction of the deformation if a high kinetic energy is introduced. The displacement of parts of the matrix body which are situated in the area of the hole through the hole or into the hole in the direction of the main deformation occurs before the residual block length is reached, the shearing off of individual layers of sheet metal in the region of the edge of the holes and the compression of the layers of sheet metal occurring essentially simultaneously, with the result that parts of the matrix body enter or pass through the hole. When the residual block length is reached, the deformation element still has a certain residual porosity. The radial deformation limiters around the matrix body are configured in such a way that they have an at most insignificant effect on the F,s profile.
One of the significant advantages of this configuration according to the invention is that, compared with the maximum deformation travel or deformation path in the presence of an end plate without a hole, i.e. not a perforated plate, the resulting residual block length with a perforated plate is reduced and, as a result, the maximum deformation travel is increased since the at least one hole in the perforated plate is dimensioned in such a way that, under the action of compressive and shearing forces, parts of the matrix body which are provided in the area of the hole are also pushed into the hole or even out of the hole when kinetic energy is introduced into the deformation element. As a result, the steep rise in force when the residual block length is reached is delayed, i.e. shifted to the right in the F,s profile, compared with a deformation element with a closed cover plate provided at its end or where the end of the deformation element rests fully against the support of the supporting structure.
The perforated plate preferably has a plurality of holes, which can be distributed uniformly or nonuniformly in the surface of the perforated plate. In this configuration, the size of the holes is preferably such that those parts of the matrix body which are provided in the area of the holes can essentially push into or through all the holes under the action of the compressive and shearing forces when kinetic energy is introduced.
The edge of the respective hole is preferably configured in such a way that it extends over as many layers of sheet metal as possible. This is necessary to ensure that the layers of sheet metal of the matrix body which are situated in the area of the edge of the hole are sheared off as a result of shearing forces instead of individual parts of the matrix body being displaced through the hole without shearing taking place. The holes are preferably provided in the outer area of the perforated plate. This likewise contributes to preventing the radial deformation limiters from having an effect on the F,s profile of the matrix body during deformation or of minimizing it. Because parts of the matrix body can be displaced through the holes in the perforated plate in the direction of the deformation, in particular in the outer area, the cavity thus created can be compressed by the lateral force that may be imposed by the deformation limiters during their deformation. This also contributes to a shortening of the residual block length.
According to another preferred exemplary embodiment, about 20 to 80%, preferably 40 to 60%, of the total area of the perforated plate is formed by holes. This ensures sufficient space through which or into which sheared-off parts of the matrix body can pass through the perforated plate when a high kinetic energy is introduced. The edges of the holes are preferably configured in such a way that they extend over at least five or at least ten layers of sheet metal. If a single hole is provided and the diameter of the matrix body is 90 mm, for example, the diameter of the hole can be about 55 mm. However, the corresponding holes in the perforated plate can differ from this as regards their configuration and size, depending on the application and the desired F,s profile.
According to another configuration, the perforated plate is preferably integrated with its edge into the support of the supporting structure, thus ensuring that adequate supporting forces are available and, on the other hand, that a high deformation energy can be introduced.
The deformation element is supported or held in the supporting structure at one or both ends, preferably in such a way that the kinetic energy to be absorbed can be introduced essentially in the longitudinal direction of the deformation element. By virtue of the construction of the honeycomb matrix body with a plurality of channels, the formation of a perforated plate with holes of defined dimensions, the thicknesses and types of material etc., there is great configuration flexibility with regard to achieving a specific dimensioning of the deformation element according to the invention for particular applications. It is thus possible to achieve a desired F,s profile.
If the deformation element is of tubular configuration, it is also referred to as a deformation tube (DEFO tube). In principle, the deformation element is constructed in such a way, by appropriate shaping and selection of the abovementioned parameters, that a maximum deformation travel is achieved for the given dimensions of the component.
Another advantage of a deformation element according to the invention of this kind is that ease of fitting and removal can be achieved through the use of a special configuration of the deformation element including its radial deformation limiters. The configuration of the respective honeycomb structure of the matrix body furthermore serves to enable load-bearing properties to be achieved, which must be ensured if the deformation element according to the invention is to be integrated or embedded into frame or supporting structures, making it possible to transmit loads at which the deformation element is capable of absorbing even the kinetic energy that occurs during impact loading. Corrosion-resistant material may be used for the deformation element according to the invention if the respective application demands it. However, it is also possible to sacrifice corrosion-resistant materials for reasons of cost and to provide the materials used for the element according to the invention with an anti-corrosion coating known per se. The strength can furthermore be influenced through the use of the respective thickness of the radial deformation limiters and the material chosen for these.
Using the configuration of the matrix body, it is also possible to influence the deformation behavior in a specifically targeted manner through the use of layers of sheet metal with transverse structures, for example. A maximum deformation travel can be achieved if the individual layers of sheet metal have holes, slots or longitudinal structures. The strength and weight of the deformation element according to the invention can furthermore be influenced in a specifically targeted manner through the use of its cell density, sheet thickness and method of winding of the matrix body. This can also be achieved, for example, through the use of oblique corrugations by using a cross-wound configuration. It is furthermore also possible to construct the matrix body in such a way that radial rigidity is reduced at the edge.
According to another exemplary embodiment, the jacketing configuration has a bead or a plurality of beads provided essentially transversely to the channels of the matrix. These beads have the advantage that, if the kinetic energy is introduced essentially in the longitudinal direction of the deformation element, the beads on the one hand have a certain initial elasticity and on the other hand represent points at which the jacket initially absorbs kinetic energy, with the sides of each bead being folded up against one another in the presence of corresponding deformation forces before the essentially smooth areas of the jacket between the beads are subjected to direct further deformation. These beads thus represent predetermined deformation points, the radial deformation limiters permitting deformation essentially only in the direction of the longitudinal axis of the deformation element.
Depending on the application and the level of kinetic energy to be absorbed, the radial deformation limiters have a wall thickness of 0.3 mm to 2.0 mm, preferably 0.5 to 2.0 mm when aluminum is used and 0.3 to 1.5 mm when steel, in particular deep-drawing steel, is used. However, a lower figure for thickness is preferred. The corrugated layers of sheet metal of the matrix body preferably have a thickness of about 0.02 mm to 0.2 mm, preferably 0.05 to 0.2 mm in the case of layers of sheet metal made of aluminum and 0.02 to 0.1 or 0.15 mm in the case of steel sheets, in particular those made of deep-drawing steel. In particular, the corrugations are configured in such a way that the matrix body has a cell density of 7.75 to 93 cells/cm2 corresponding to 50 to 600 caps (cells per square inch).
The matrix preferably includes, in a manner known per se, packed flat layers of sheet metal or an essentially cylindrically wound assembly formed by a spiral, an involute shape or S shape for instance. The individual layers of sheet metal resting upon one another in the assembly can but need not be brazed together in the areas of contact.
According to another embodiment, the cell density of the matrix body is varied from section to section in the longitudinal direction. This is achieved, for example, by inserting additional layers of sheet metal with shallower corrugations or more widely spaced corrugations than in the corresponding adjacent section between essentially smooth layers of sheet metal, the smooth layers of sheet metal of the section with the lowest cell density preferably being provided so as to be continuous in the longitudinal direction of the matrix. It is also possible to vary the cell density of the matrix in the radial direction by winding up a layer of sheet metal with a corrugation frequency that increases continuously in one direction to form an essentially cylindrical honeycomb structure, for example.
According to another embodiment, the layers of sheet metal of the matrix have bead-like structures essentially transversely to the direction of the channels, these structures also being referred to as transverse structures. These transverse structures serve to ensure that when a sufficiently high kinetic energy is introduced, deformation within the matrix body starts initially at the transverse structures in order in this way to ensure an as uniform as possible absorption of the kinetic energy by the matrix body. These transverse structures are preferably provided at a spacing of from 2 mm to 20 mm.
According to yet another exemplary embodiment, the layers of sheet metal of the matrix body by which the channels are formed have within the channels laterally offset channel sections, also referred to as longitudinal structures. These longitudinal structures thus do not provide continuous channels but discontinuous channels, with the result that the matrix body has within it a structure corresponding to a turbulence cell structure or plate-fin structure, as used inter alias for heat exchangers. These longitudinal structures have the advantage that the kinetic energy-absorbing properties of the deformation element according to the invention can additionally be influenced in a specifically targeted manner through the use of the length of the channel sections offset section by section. This provides a further parameter for influencing the F,s profile to suit the specific application.
Preferably, it is also possible to provide the corrugations of the layers of sheet metal in a curved or herringbone configuration or as a combination of the two. Through the use of such curved corrugations or herringbone-configuration corrugations on the layers of sheet metal, it is possible to achieve a specific distribution of the deformation-inducing forces introduced into the interior of the matrix body, thereby likewise enabling the F,s profile to be influenced in an application-specific manner.
According to another exemplary embodiment of the invention, the matrix body or its channels is (are) preferably filled with a foamed material, the foamed material preferably being a foamed plastic, in particular a corrosion-inhibiting foamed plastic. On the one hand, this prevents corrosion from occurring within the matrix and the radial deformation limiters if stainless steel is not used, for example, such corrosion potentially having a disadvantageous effect on the deformation properties. On the other hand, it is also possible, by the selection of an appropriate foamed plastic with defined properties, to influence the absorption capacity for kinetic energy in the element in a specifically targeted manner, with the result that it is also possible to influence the F,s profile by introducing a foamed material.
The F,s profile of the deformation element can preferably be made essentially constant, at least in one section, preferably in a large section and, even more preferably, in its entirety through the use of a suitable multiplicity of predetermined deformation points in the deformation element. If, for example, a multiplicity of predetermined deformation points with different kinetic energy-absorbing properties is provided in the deformation element, it is also possible to provide at least one section in the F,s profile which rises progressively.
With regard to a maximum deformation path or deformation travel to be achieved relative to a defined overall length, the deformation element is configured in such a way as regards its deformation behavior that the maximum deformation travel is from about 60 to 200 mm. Depending on the application, the deformation travel can also be less than or greater than the range stated.
According to another exemplary embodiment of the invention, the matrix body has cavities formed by walls, the walls being part of the respective layers of sheet metal from which the matrix body is constructed. The deformation element is preferably secured on the supporting structure in such a way that forces developed during an impact can be introduced into the walls at an angle to a main direction of extension of the latter.
The cavities are preferably also configured as channels which, for example, extend coaxially to the longitudinal axis of the matrix body. When a deformation element with a matrix body of this kind is secured on the supporting structure in such a way that the forces introduced during an impact act essentially in the direction of the walls, the deformation energy is absorbed inter alias by the fact that the walls are subject to a buckling load. This results in a relatively sharp rise in the F,s profile immediately after the introduction of the kinetic energy. This steep initial rise or initial peak in the F,s profile has the effect that relatively high deformation forces are introduced into the supporting structure via the deformation element before the latter is deformed and thereby absorbs kinetic energy. As a result, the supporting structure may undergo plastic deformation due to the peaks in the deformation force. However, this is to be avoided.
In accordance with another feature of the invention, the deformation element has a longitudinal axis. The honeycomb matrix body includes at least one at least partially structured sheet metal layer. The at least one at least partially structured sheet metal layer forms a structure with walls having a main direction of extension extending at an angle with respect to the longitudinal axis. The structure with walls is a looped structure, a wound structure or a stacked structure.
In accordance with another feature of the invention, the support assembly with its deformation element is used in a bumper system of a motor vehicle.
According to the invention, the deformation element is configured or provided relative to the supporting structure in such a way that the forces developed during an impact are introduced at an angle to the main direction of extension of the walls, the direction being defined in relation to the longitudinal axis. By introducing the forces obliquely in this way, it is ensured that the walls can be deformed more easily, in particular at the onset of deformation, into the cavities, with the result that the initial peak in the F,s profile is at least greatly reduced. Through the use of a deformation element of this kind according to the invention, the initial region of the F,s profile too can thus be influenced in a specifically targeted manner to give an improvement in the absorption of kinetic energy introduced.
The main direction of extension of the layers of sheet metal forming the walls is preferably provided at an angle to the longitudinal axis. This can be achieved, for example, by winding the individual structured layers of sheet metal obliquely. If the main direction of extension of the walls forms an angle with the longitudinal axis, the deformation element can be secured on the supporting structure in such a way that the longitudinal axis is provided essentially perpendicular to the support or support region on the supporting structure.
However, it is also possible to use a conventional matrix body, the main direction of extension of the walls of which is essentially coaxial with the longitudinal axis of the matrix body, the matrix body being secured on the supporting structure in such a way that the longitudinal axis is provided at an angle to the support on the supporting structure.
In accordance with another feature of the invention, the deformation element has a front side. The supporting structure has a support region provided at the front side. The honeycomb matrix body has a longitudinal axis extending at an angle other than 90xc2x0 with respect to the support region.
In accordance with another feature of the invention, the honeycomb matrix body is a conical matrix body or a frustoconical matrix body.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a support assembly with a deformation element with radial deformation limiters, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.